The present invention relates to reduction of the chlorohydrin content of a product obtained from protein hydrolysed with hydrochloric acid.
As is known, hydrolysing protein with hydrochloric acid leads to formation of certain undesirable chlorinated by-products which have come to be known generically and commonly as chlorohydrins, or .alpha.-chlorohydrins, which include mono-chloropropandiol, i.e., 3-chloro-propan-1,2-diol, and di-chloropropanol, i.e., 1,3 dichloropropan-2-ol, compositions. Desirably, it is sought to provide hydrolysed protein obtained by hydrolysis of protein with hydrochloric acid which contains chlorohydrins in an amount of below 1 ppm.
Various means and methods have been proposed and employed to reduce the chlorohydrin content of protein hydrolysed with hydrochloric acid, including subjecting a liquid containing the hydrolysed protein to a steam distillation process, as disclosed in U.S. Pat. No. 4,759,944. It also is known that the chlorohydrin content may be reduced by adjusting the pH of the hydrolysed protein, which is acidic, with an aqueous alkali composition to a pH of from about 8 to about 14 and holding the pH-adjusted hydrolysed protein for a time sufficient to reduce the chlorohydrin content, as described in European Patent Application No. 88118189.3 and its counterpart U.S. application Ser. No. 07/258,191.
It has been known to us that the alkaline treatment process disclosed in the above-noted European and U.S. applications can be carried out readily in bulk in a batch-wise process. However, it was found that, particularly at chlorohydrin reduction reaction temperatures of from about 35.degree. C. to 55.degree. C., as exemplified in the European and U.S. applications, holding the quantities of hydrolysate produced by commercial scale hydrolysis equipment in bulk batches results in holding times on the order of hours and requires what may be considered to be uneconomical amounts of facility workspace to match production efficiency of the hydrolysate production step.
To address the problem, it was sought further to employ the knowledge disclosed in the European and U.S. applications that as the temperature of the chlorohydrin reduction reaction is increased above ambient conditions, the reaction induced by the added alkali requires less time to achieve an equivalent amount of chlorohydrin reduction. However, it was found that chlorohydrin reduction reaction temperatures of from about 70.degree. C. to 80.degree. C. still required holding times on the order of hours and that as reaction temperatures approach 100.degree. C., quantities of ammonia gas are produced which, as a practical matter, must be removed from the workplace. As is apparent, collection and disposal of the ammonia gas requires additional methods and means.
Thus, our efforts have been directed to increase the efficiency of reduction of the chlorohydrin content of hydrochloric acid-produced hydrolysed protein in a commercial environment on a scale which is compatible with the production efficiency of generally available hydrolysis means and methods and to address the problem of production of ammonia gas in an alkaline chlorohydrin reduction reaction.